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Discharges to water and sewage sludge production in 2018

Discharges of phosphorous have increased

Statistical news from Statistics Sweden and Swedish Environmental Protection Agency 2020-07-01 9.30

In 2018, total discharges of nutrients to water via municipal wastewater treatment plants subject to authorisation amounted to 270 tonnes of phosphorous, 15 000 tonnes of nitrogen, 6 500 tonnes of biochemical oxygen demand (BOD7), and 40 500 tonnes of chemical oxygen demand (COD-Cr), including some wastewater overflow at the plants.

Table 1. Discharges from municipal wastewater treatment plants in 2018, by sea basin district, and total biannually 2008-2018
Sea basin districtTot-PTot-NBOD7COD-Cr
Bothnian Bay 12 1 307 622 2 061
Bothnian Sea 33 3 508 1 160 5 133
Baltic Sea 121 6 020 2 367 19 599
The Sound (Öresund) 30 926 542 3 138
Kattegat 65 2 990 1 741 9 907
Skagerrak 5 232 116 646
Total 2018 266 14 982 6 548 40 483
Total 2016 237 15 414 6 612 35 257
Total 2014 260 15 743 7 549 44 496
Total 2012 275 17 120 7 993 47 264
Total 2010 267 17 419 7 908 46 510
Total 2008 313 18 433 7 447 46 893

Discharges from municipal wastewater treatment plants decreased compared with 2016, in spite of an increased load with regard to phosphorous and BOD7. The average removal rate for nitrogen remains unchanged at 62 percent, while it increased slightly for phosphorous and BOD7.

Since 2016, discharges from municipal wastewater treatment plants increased with regard to phosphorous and COD-Cr, while discharges of nitrogen and BOD7 decreased. In a ten-year perspective, there is a trend of decreasing discharges among all parameters.

Table 2. Quantities of phosphorous, nitrogen and BOD7 in incoming wastewater and outgoing, treated, effluent and corresponding rate of removal, biannually 2008-2018
 PhosphorousNitrogenBOD7
 InOutRate of removalInOutRate of removalInOutRate of removal
 tonnestonnes%tonnestonnes%tonnestonnes%
Total 2018 5 351 266 95 41 294 14 982 64 224 533 6 548 97
2016 5 546 237 96 41 049 15 414 62 215 488 6 612 97
2014 5 176 260 95 41 340 15 743 62 208 340 7 549 96
2012 5 307 275 95 41 967 17 120 59 196 706 7 993 96
2010 5 563 267 95 42 292 17 419 59 202 100 7 908 96
2008 6 346 313 95 42 360 18 433 56 202 717 7 447 96

Agricultural use is now the most common use of sewage sludge

Use on agricultural land remains the most common application of sewage sludge from municipal wastewater treatment plants since 2016. In 2018, total sewage sludge used in agriculture was estimated to be around 83 000 tonnes of dry substance, corresponding to 39 percent of total net production. This is five percentage points more than in 2016. Plant soil use was the second most common use of sewage sludge, with 54 000 tonnes, corresponding to 26 percent of total net production, which is one percentage point less than in 2016. The third most common use was as landfill cover to establish a plant layer, with 36 200 tonnes, corresponding to 17 percent of total net production, which is five percentage points less than in 2016.

Wastewater treatment plants’ estimated production of sewage sludge (dry substance) was around 212 000 tonnes in 2018, which is 3.6 percent more than in 2016.

Table 3. Sewage sludge production and use in Sweden, biannual 2008–2018
  Sewage sludge use categories (tonnes)
  FarmlandForest landPlant soil, normal PPlant soil, high PLandfill coverIncineration without P extractionIncineration with P extractionLandfillOther useStorageUse not specified
2018 211 604 82 288 137 26 271 27 768 36 199 2 816 0 2 299 21 095 12 466 265
2016 204 253 69 506 150 23 908 31 733 44 506 4 154 0 3 060 14 368 11 157 1 711
2014 200 510 50 950 570 20 130 38 980 47 520 1 790 380 3 560 20 040 13 650 2 940
2012 207 460 48 340 1 280 25 510 41 140 47 450 1 290 190 7 130 23 580 2 470 9 080
2010 203 520 50 460 1 680 26 710 38 500 41 490 2 220 230 7 540 17 260 17 390 40
2008 213 790 55 640 1 920 17 580 40 510 42 510 330 130 6 240 15 180 6 790 26 990

Concentrations of nutrients, metals and organic indicator substances in sewage sludge from municipal wastewater treatment plants, by municipal wastewater treatment plant class size, are given in table 4.

Table 4. Concentrations of nutrients, metals and organic indicator substances in sewage sludge from municipal wastewater treatment plants
 Average values, mg/kg TS
 Population equivalent (pe)
 –19 999  20 000–99 999100 000– Total
    201820162014201220102008
Phosphorous 18 270 25 288 31 617 26 500 26 857 26 360 26 410 27 640 27 740
Nitrogen 36 552 44 243 51 950 45 934 45 330 45 150 43 010 44 080 42 590
Cadmium 0.7 0.8 0.7 0.7 0.8 0.9 1 0.9 0.8
Chromium 17.6 26.5 21.5 22.1 23.1 24.2 28 28.8 28.3
Copper 270 323.9 374.6 335.3 342.8 348 352.7 347.3 335.3
Mercury 0.4 0.4 0.5 0.5 0.5 0.5 0.6 0.6 0.6
Nickel 11.8 16 19.8 16.8 16.5 16.3 17.4 16.6 16.9
Lead 13.7 16.7 17 16.2 16.1 19.4 22.1 21.9 22.4
Zink 486.3 585.4 587.3 562.5 572 568.2 601.5 570.1 544.3
Nonylphenol 2.6 3.5 5.8 4.3 6.4 7.2 8.6 10.3 10.6
PAH 0.34 0.48 0.88 0.63 0.68 0.85 0.88 0.94 0.98
PCB 0.01 0.02 0.02 0.02 0.03 0.05 0.04 0.04 0.05

The statistics are now available in the statistical database

The statistics published in the Statistical Reports on 2018, 2016, and 2014 are now available in Statistics Sweden’s Statistical Database. There, the tables can be tailored to the user’s needs by selecting specific variables and groups. It is also possible to export the statistics to other file formats for further analysis and to use Statistics Sweden’s API for automated data requests.

Publication

More detailed statistics about discharges to water from municipal wastewater treatment plants can be found in the Statistical Report Discharges to water and sewage sludge production in 2018.

Statistical Database

More information is available in the Statistical Database

Feel free to use the facts from this statistical news but remember to state Source: Statistics Sweden.

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Swedish Environmental Protection Agency

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Statistics Sweden, Environmental accounts and Environment

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Alexander Dimberg

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